Antibodies to streptococcal carbohydrate: substitutes for the myeloma proteins.

Antibodies to streptococcal carbohydrates have been employed in a number of ways as substitutes for the myeloma proteins in studies of the structures of antibody molecules and the development of the immune response. This review concentrates on the chemical nature of the streptococcal polysaccharides and on structural studies of the variable regions of the light chains of rabbit anitbodies to the group A-variant polysaccharide produced by hyperimmunization. The chemistry of the group A-variant polysaccharide has now been clarified, and this information has explained the frequently reported difficulty in the preparation of precipitating antisera to this antigen. The group A-variant vaccine is a potent antigen, but the bulk of the antibody is nonprecipitating because it is directed against the noreducing terminal sugar of the nonbranched rhamnose polymer. Chemical studies of the light chains of homogeneous rabbit antibodies reveal two hypervariable regions and a J sequence that joins the variable region to the constant region. Although the precise topographic highlights of the antigen-binding site hae yet to be determined, these structural studies have extended our knowledge of the structure and diversity of antibody molecules.